Electrical musical instrument



Feb. 28, 1950 briginal Filed Nov. 2a, 1943 3 Sheets-Sheet 1 w 4 N x n a b 1 f v 1.. J, 3

. [rm/ex? for a lauregsgammona s Sheets-Sheet 2 HAMMOND ELECTRICAL MUSICAL IiISTRUMENT 9Q v 9Q 58 Feb. '28, 1950 Original Filed Nov. 26, 1943 L. HAMMOND ELECTRICAL MUSICAL INSTRUMENT Feb. 28, 1950 3 Sheets-Sheet 5 Original Filed Nov. 26, 1945 Reissued Feb. 28, 1950 ELECTRICAL MUSICAL INSTRUMENT Laurens Hammond, Chicago, Ill., assignor to Hammond Instrument Company; Chicago, Ill. a corporation of Delaware.

Original No. 2,480,131, dated August 30, 1949, serial No. 511,795, November 26, 1943. Application for reissue September 28, 194 9, Serial-No.

17 Claims. (01. 's4-1.14.=)

Matter enclosed in'heavy brackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additions made by reissue My invention relates generally to electrical musical instruments and more particularly to improved means for generating electrical signals corresponding to musical tones. I

It is an object of my invention to provide improved electrical signal generators for musical instruments which are capable of producing musical tones of complex quality and containing a large number of the higher harmonics in substantial amplitude.

A further object is to provide an improved electrical musical instrument which may be operated by means of a pedal clavier, and in which theintensity of the tones produced is responsive to the velocity of pedal depression.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figures 1a and 1b together constitute a wiring diagram of the instrument and also include a vertical sectional view of the pedal action;

Figure 2 is a front elevational view of a modified form of the invention;

Figure 3 is a transverse sectional view taken on the line 3--3 of Fig. 2 and Figures 4, 5 and 6 are fragmentary details showing modified forms of generator springs.

Referring to Figs. 1a and 1b the invention is diagrammatically illustrated as incorporated in a pedal-operated instrument comprising a plurality of natural pedals Ill and sharp pedals I2 extending throughout a limited range, such as an octave. These pedals are mounted for pivotal movement on a fulcrum [4 carried by a base l5,

and are operable through the range indicated by the dotted lines in Fig. la, the extent of the depression of the keys being limited by a strip it of felt or the like. The pedals may be returned to normal position from their dotted line position either by gravity as illustrated in Figs. 1a and lb, or by resilient means, such as the leaf spring I80 shown in Fig. 3, the pedals being shown in full lines in their normal posit-ions, in which they rest upon a stop ll! of felt or similar material.

Each of the pedals H1, I2 carries a member 20 into which a pivot stud 22 is threaded, this stud being secured in adjusted position by a lock nut 24. A hammer 26 is carried at the end of a shank 28, the shank terminating in a butt portion 30 pivoted to the stud 22. An adjustable escapement button 32 is threaded in the butt 3!! and is adapted to engage the upward extension 34 of a resilient latch 36, the latter having a shoulder 38 forming a bearing surface for a rearwardly extending car 40 of the butt 30.

The hammer shanks 28 normally rest against a feltpadded action rail 42. A hammer check 44 is positioned to check the return fall of the hammers.

This action is similar to well known piano actions and operates in a well known manner. When the pedal is depressed the raising of the rearward end of the pedal causes the hammer to swing about the shoulder 38v as a pivot until the button 32 strikes the latch extension 34 whereupon the resilient latch is flexed to its dotted line positionpermitting the hammer to rebound freely and come to a temporary rest position, against the check 44, the-parts being returned to their normal position shown in Fig. 1a upon release of the depressed pedal. In lieu of the action described any other suitable simple piano type action may be used.

Each of the hammers 26 is positioned to strike one of aplurality of brackets 46, which form the lower anchorages for helical springs 48, the upper end of each of these springs being secured to a complementary bracket 50. The brackets 46 and 50 are secured to a rigid plate 52. The plate 52 is suitably securedto the base plate l'5.

Above each of the brackets 46 there is an electromagnetic pickup '56, while similar electromagnetic pickups 58 are located above the brackets .50. Each of these pickups comprises a coil 60 surrounding a permanent magnet 62. The coils B0 of the pickups .58 are connected in series between ground and one end of the primary winding 64 of an input transformer'fifi, while the windings of the pickups 56 are connected in series between ground and a switch arm 68 cooperable with contact points 10, II and '22, the latter being'respectively connected to the un'g-rounded'terminal of the primary winding and intermediate taps thereof. The secondary winding 16 of the transformer 64 has one terminal thereof grounded and its other terminal connected to the control grid 18 of a preamplifier tube 86 which maybe a pentode of the 6J'7G type.

The cathode 8.1 of the tube 8015 connected to its suppressor grid '82 and is connected to ground through a. self-bias resistor R84 and a by-pass condenser C88. The plate 88 of the tube .80 is connected to a suitable sourc of plate voltage, indicated as a terminal +250 v., through a potentiometer loadresistance R911. The plate 88 is connected to ground through a filter condenser 'C92'whi-1e'the screen grid 94 is connected to the +250 v. terminal through a voltage dropping resistor R96, and is connected to ground through a filter condenser C98.

' a decay resistor RI 56.

A slider I cooperable with the potentiometer resistance R90 forms a volume control and is connected through a blocking condenser CI02 to the bracket 46 the connectedspring 48 is shockthe grid I04 of a triode I06 which may be of the 6J5G type.

I06 is connected to ground through a' self-bias The cathode I08 of the triode resistor RI I0 and by-pass condenser CI I2 while the plate II4 of this tube is connected to a suit-' able plate current source indicated as a terminal +250 v. through a load resistor RI I6. The output of the triode I06 is transmitted to the primary winding II8 of a coupling transformer I20 through a blocking condenser CI22, the primary winding being shunted by afilter condenser CI24.

The terminals of the secondary I26 of the transformer I20 are respectively connected to the grids I28, I26 of amplifying and control pentodes I30, I 3| forming the first stage of a push-pull amplifier. The cathodes I32, I33 as well as the suppressor grids thereof are connected to ground excited into vibration. This spring will transmit the shock wave at a velocity which is dependent ;upon the physical dimensions of the spring, and

upon the properties of the wire of which it is made. The spring is preferably made of piano steel wire. The ends of the spring are hooked to the brackets 46 and 50 and are under sufby the hammer is imparted to the lower end of the spring, and progresses upwardly, the wave being substantially completely reflected at the while the screen grids I34, I35 are connected to a suitable potential source indicated as a terminal +100 v. The plates I36, I31 of the pentodes I30, I3I

through blocking condensers CI44 and CI45 re 'spectively. The output of the push-pull amplifier tubes I42, I 43 is supplied through an output transformer I48 to a speaker I50. The pen- 6K6G type.

The condensers C86, CI02, CI I2, CI44 and CI45 are of such values relative to the parameters of the amplifying system that frequencies below? 'todes I and I3I are preferably of the 6K7G 1' type, while tubes I42 and I43 may be of the those of the lowest pitch musical tone to be pro- 'duced are appreciably attenuated, thus substantially eliminating from the output of the ampli "fier low frequency thumps, produced in the pickare connected through load resistors RI38, RI39 to a plate voltage source illustrated up coils incidental to the hammers 26 striking? the armatures or supports 46. Condensers C92, CI24, CI40 and CH1 are of such values as to limit the voltage for the suppression of undesirable high frequency harmonics and distortion terms. In addition the gain of the amplifying system is controlled in the following manner.

The center tap I54 of the secondary winding I26 is connected to ground through a condenser Cl56 and is connected to a source of cutoifbias potential, indicated as a terminal v., through The center tap I54 is adapted to be connected to ground upon the depression of anyone of the pedals through an attack resistor RI62 and one of a plurality of switches I64. There is a switch I64 arranged beneath each of the pedals I0, I2 and resiliently biased to close upon the depression of its associated pedal, the switch being held in open position, when the pedal is in its undeqpressed position, by an insulating actuator I66 attached to each of the pedals. I The switches and their actuators are so arranged that the hammer 26 will strike its associated bracket 46 just prior to the closure of the switch I64. Thus the trantial by virture of their connection to the -50 v. terminal through the resistor RI 28. I

When a key is depressed and its hammer strikes transmission line.

junction of the upper end of the spring and the bracket 50. This reflection is nearly complete because of the impedance mismatch between the spring and the brackets 46, 50. Obviously some of the energy transmitted by the spring is transferred to the brackets 46 and 50 and they are thus moved sufiiciently to excite the pickups 56, 58.

It will be noted that the impulses transmitted back and forth by the spring strike the brackets 46 and 50 in 180 degrees out of phase relation. Thus when the switch 68 is positioned to engage contact I0 the signal impressed upon the primary winding 64 is effectively twice that of the frequency generated by the spring and thus the tone produced is effectively an octave higher than when only the pickups 58 are coupled to the output. By shifting the switch 68 to connect to one of the intermediate taps of the transformer winding 64, the degree of such octave coupler effect may be adjusted whereas when such coupler effect is not desired the switch 68 may be adjusted to its off position, thus utilizing only the pickups 58 for the generation of the signal.

The operation of the coil springs 48 as tone generators differs materially from the generation of musical tones by piano and similar strings, for in the latter the vibrations are transverse, whereas in the coil springs the waves are compressional. The springs 40 have the desirable characteristic that the shock wave is transmitted and reflected in a linear manner, resulting inthe production of desirable harmonic and enharmonic partials.

The springs 48 operate in the manner ofa The frequencies generated are substantially independent of the tension on the springs. The tension should be sufficient merely to prevent contact of adjacent turns and to maintain the ends of the springs in firm contact with velocity of transmission is given:

pi I Winn 2p in which:

With a spring. having the variables of the foregoing formula of given value, the fundamental frequency (f) generated will depend solely, upon the length (L) of the spring in accordancewith the relation: f=v1/L.

asgaoo Thus there is practically no tendency'ior' the springs to getout' oftune: Assuming that the springs are protected against corrosion; they should maintain theinrespective musical pitches indefinitely. 7

By virtue of the fact that' the spring is-shock excited at its extremity, the tones produced are of high harmonic development,v generally-- with the harmonics decreasing progressively irrampli tude. Furthermore; as'the tones-decay; thehigh= er harmonics decay more rapidly thansthewi'undamental. This" effect is pleasing and is common to the tones of the pianoandother' percussive and. pluckedstring instruments.

The character'of the armaturesmr springsupports 46, 50 will determine; inpart, the quality and decay rate of the tone produced'. These sup ports should be relatively stiff and? should be firmly attached to the'pl'ate 52, whilethe latter should be rigid and haveconsiderablem'ass.

ment of the invention the natural keys HI and "sharp keys I2 are respectively secured to'leaf springs I80 which rest upon a fulcrum rod ['82,

the leaf springs having their'ends anchored to'a cross bar IM'by means of adjustable bolts I85. The leaf springs I801 normally hold the pedals I 0 and I2 in engagement with an up-stop. strip I88, of. felt orthe like, which is secured to; the front wall I90 ofthe. instrumentcase. Theremainder of the caseiis formediby'a single; sheet I92 which is bent toziornr a; base plate I94", an inclined rear wall I96 and atop H18. A pair of: opposed channels200, 201' are-riveted tothe; top I98, the channel 201 also being riveted" to the front wall I90. A plurality of pickup magnets 202, 203 are. adjustably" secured inxbushings? 204' which are secured" to the top 98; the pickup magnets 202,203 carryingpickup'coils 206.

Spring supports 208-, 209'. areriveted respectively'to the lower flanges:- 0t channels 200;. 2lll so as to lie adjacent'thelower ends of'the imagnets 202. 203 Coil springs: 25); 211i arerrespec-- tively hooked to? thesupportsf 2llBf-an'd 209' at. their upper ends and their-lowerrendsare hooked to one of a. plurality of pivoted armsq2l3. The arms 2l3z' are preferably madeofi' an: aluminum or magnesium. alloy and are: preferably channelshaped to secure maximum. strength. with; minimum mass. The: arms2l3 are= pivoted-on a rod 215 carried by'a' fixed rail H55, and are normally' held against a soft felt. step 218: carried by the rail 216 Each of the pedals: I0, I25 has an inverted L-shaped hammer 220 secured thereto, these hammers being of. substantial mass; To prevent the generation of tones in which" the very high harmonics predominate, the. hammer 2211, if made: of: metal, may havera thin padi 22l' of softer material, such as" leather, secured to its striking face.

It will be noted that the springs 210, 21! are shown as being of di'fierent-di'ameters'to illustrate-that they difler fromonewanother will.

- upper support 209.1 and an arm H3.

generate tones of difierent pitch; It: will be" understood that the springs may be of different lengths or that other of their physical proper ties may'difier tocause'them 'to generateton es of different fundamental pitch; It will be assumed that the springs 210 and 2i l have such different physical properties that they will. generateitones of octavely related pitch.

Upon depression of one of the pedals l0, 12 its hammer 220 strikes the underlying endof its associated arm 2H andswingsthe latter away from thedamping stop 2 l8. The striking of the hammer 220 against the arm 2| 3. shock-excites thesprings' 2H1, 21H, the amplitudes of the compressiona'l waves: producedv in. theseasprings being dependent'upon the velocity of pedal depression. As long asthe pedal. is held depressed, the compressional. waves willbe reflected at the: lower ends of the: springs, since the hammer 220 has suificient mass and rigidity to provide a point of considerable. reflection- The supports 208-, 209 are of'suflicient stiffness and the channels 200, 2M are of'suilicient mass" and rigidity: that reflection of a high. percentage of the energy'of the Wave also takes placeiat the upper ends-of the :springs.

Since the springs2l0, 2H generate tones. differing in pitch by anoctave and the signalsproduced thereby are combined in'the output circuit of the instrument, it willlbe apparent that the musically desirable octave; coupler efiect; is obtained The degree of octave? coupler effect may be determined by adjustment of 'the-zspacing of. the lowerendstof the pickup magnets 202, 203. from the'spring supports 208, 209 respectively: Furthermore; the quality of the rnusical'tones produced may be controlled by well known means for modifying electrical signals in the amplifier and output systemof the instrument.

The pickup coils206 may be coupled directly to an amplifying an'd'electroacoustic translating system such as a public address system. .or' may be coupled in the manner shown .in Figs. laand lb to an amplifier and speaker-individual. to the instrument. The. volume control is not absolutely essential, since the intensity of the tones may be determined, within a fairly wide range, by the velocity of pedal. depression.

Although only two springs are illustrated as being attached to each of the pedals l0, l2; it may be desirable in some instancesto employ more than'two: springs so as to' produce. chordal effects. Furthermore, the transmission charac teristicsofrthespringsimay be varied by the addition of'suitablelumped impedances to provide additional. points of: reflection withinthe spring itself and thereby'alterthe harmonic content of the tones" produced.

Several such variations: in the. form, of. the springsiareiillustrated. in Figs.- 4, 5,, andrfi. InEig. 4. the: spring; transmission linev comprises: two springs'2'2'4, 2250f the same wave propagation velocities which are. hooked together between. an

This combination of springs will produce an octave coupler effect; since: the junction between the two springs provides an. additional. point of partial reflection. due to the impedance mismatchoi. the

1 twospringsi: Thesdegree ofiimpedancemismatch offthe twosprings will 'afiectthe relative-intensities of the fundamental andoctave tones.

In Fig: 5 the generatorcomprises two similar springs 226 221 conneoted together" by allinle228 'llfofi, substantial. mess. I The; link; 22.8: serves aa a :the compressionwaves with the result that the tone produced will be of different quality than if the springs 226, 221 were formed as a single integral spring. The link-229 tends to pass the lower frequencies and to reflect the higher frequencies; Since the impedance of link 228 varies with the frequency, certain harmonics will be intensified more than others. The tone produced will have a characteristic initial tone quality and its quality will change as the tone decays due to the more rapid attenuation of the higher frequencies. In this respect the tones will be similar to those of the piano and to the tones of other percussive mechanical musical instruments in which the tones have substantial d ecay periods.

In Fig. 6 the generator comprises a spring 230 having a purality of sections 232. Small masses 234 of solder or the like are secured to the spring at the junctions of the sections 232 to provide a plurality of points of reflection for the compressional waves. The size of the masses 234 will determine the character of the tones produced,

that is, if the mass is small it will transmit more ofthe lower frequencies and reflect, to any appreciable extent, only the highest frequencies. As the weight of the mass is increased the lower frequencies are progressively transmitted less and reflected to a greater extent.

The sections 232 may be of equal or different lengths, or diameters, or both, and the masses 234 may be of equal or diflerent sizes. Byproper selection of these variables, any one of a wide rvariety of different tonal effects may be obtained.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that numerous modi- 'fications and variations may be made in the form and construction thereof, without departing from the more fundamental principles of the invention. I therefore desire, by the following claims,

to include within the scope of my invention all such similar and modified forms of the apparatus disclosed, by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

-I claim:

1. In an electrical percussive tone musical instrument, the combination of a playing key, a

"pair of supports, a coil spring carried by said, supports, key operated means to produce a single shock excitation of said spring for each key de- 2. In an electrical percussive tone musical insstrument, the combination of a pair of spaced armatures, a coil spring carried by and extending "between said armatures, means to shock excite said spring to cause a compressional wave in said spring which is-reflected by said armatures and thus travels back and forth through said spring,

'and an electical means adjacent each of said armatures for sensing said waves and translating them successively into electrical impulses and into sound.

3. In an electrical musical instrument, the

combination of a playing key, a coil spring, means operated by the key to produce a single shock excitation of said spring upon each key depres- -"sion to cause a compressional wave therein, -means to support said spring for substantially.--

complete reflectlon of compressional-waves at the ends thereof, and electrical means for sensing thevibrations in said spring.

4. In an electrical musical instrument for-the production of percussive musical tones, the combination of a coil spring, means to shock excite said spring to cause a vibrational wave therein,

means to support said spring at both ends for substantially complete reflection of waves at the ends thereof, an electrical means at each end of said spring for sensing the vibrations thereof,

.and means for selectively utilizing the output of said electrical sensing means.

5. In an electrical musical instrument, the

combination of a helical coil spring, means sup- "porting said spring at at least one end thereof,

means capable ofimparting a single blow to said spring to produce a wave repeatedly traversing said spring by being reflected at the ends thereof,

and an electrical pickup located adjacent said spring and "capable of translating the waves "therein into electrical waves.

6. In an electrical" percussive tone musical instrument, the combination of a helical coil spring,

means supporting said spring at at least one end thereof, means capable of imparting a single blow to one endof said spring to produce a compressional wave repeatedly traversing said spring by being reflected at the ends thereof, and an electrical pickup located adjacent said spring and capable of translating the compressional waves "therein into electrical waves.

' 7. In an electrical percussive tone musical inincluding amplifying and electroacoustic translating means, the combination of a plurality of keys for operation by the player, a

plurality of coil springs associated respectively with said keys, means operated by said. keys to apply a, single shock excitation thereto upon each operation of the key and of degree responsive to velocity of key operation, electrical pickup means associated with said springs, and means coupling said pickup means to the amplifying and electroacoustic translating means.

8. In an electrical percussive tone musical instrument including amplifying and electroacoustic translation means, the combination of a plurality of pedallyoperated keys, a plurality of coil spring associated respectively with said keys, means operated by said keys to apply a shock excitation to the extremities of said springs of degree responsive to velocity of key operation to produce compressional waves in said springs, there being but a single shock applied to a spring upon each operation of a key, electrical pickup means associated with said springs, and means 3 coupling said pickup means to the amplifying and electroacoustic translating means. I

9. In an electrical percussive tone musical instrument having "a signal transmission system terminating in electroacoustic translating means, the combination of a plurality of supports, a

pedal, stops for limiting the extent of movementof'said pedal, a light weight pivoted arm,

- coupled to, said signal transmission system.

10. In an electrical musical instrument for playing bass accompaniment tones and having 9 an output system including an amplifier and electroacoustic translating means, the combination of a plurality of pedals, a plurality of coil springs, at least one for each of said pedals, means supporting at least one end of each of said springs, means operated by said pedals to shock excite said springs to produce compressional waves therein, said means operating to produce a single shock-excitation of its associated spring for each pedal depression, and mechanico-electric translating means responsive to the Waves in said springs and coupled to said output system.

11. In an electrical musical instrument, the combination of a coil spring, a manually operable key to produce a. single shock-excitation of said spring by a blow at one end of the spring directed longitudinally of the spring to produce [to] a compressional wave therein and means for electrically sensing the waves produced in said spring by such shock excitation.

12. The combination set forth in claim 11 in which said coil spring is divided into a plurality of sections with means providing points of reflection between the sections.

13. The combination set forth in claim 11 in which said coil spring is in a plurality of sections of differing dimensions so as to have different velocities of wave transmission.

14. The combination set forth in claim 11 in which said coil spring is in two equal sections, and in which the sections are joined by means providing points of wave reflection.

15. The combination set forth in claim 11 in which the coil spring is tensioned between a resilient arm and a movable arm, in which said manually controllable means strikes the movable arm, and in which the sensing means is responsive to vibrations of the resilient arm.

16. A percussive musical tone signal generating 10 apparatus for electrical musical instruments, comprising a coil spring system incorporating means for reflecting compressional waves, said means being located to cause the system to produce a wave corresponding to two complex musical tones in octave relationship, means to produce a single shock-excitation of said coil spring system upon each key depression to initiate com-- pressional waves therein, and electrical pickup means located adjacent the spring system so as to be responsive to the compressional waves therein.

17. Apparatus for generating a signal corresponding to a percussive musical tone comprising,

REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS Number Name Date 1,409,657 Boynten Mar. 14, 1922 2,187,251 Severy Jan. 16, 1940 2,254,284 I-Ianert Sept. 2, 1941 2,266,030 Hammond Dec. 16, 1941 2,286,587 Sundt June 16, 1942 2,321,366 Demuth June 8, 1943 2,357,191 Hanert Aug. 29, 1944 

